This invention relates to gas turbine power plants and particularly to a closed cycle using helium as the working medium and contrarotating rotors of both the compressor and turbine, and particularly where the heat source is a nuclear power plant.
U.S. Pat. No. 3,363,831 granted to M. R. Garnier on Jan. 6, 1968 discloses a contrarotation axial flow gas turbine power plant and U.S. Pat. No. 3,791,137 granted to A. Jubb and D. E. Williams discloses a closed-cycle gas turbine power plant using helium as a working medium.
I have found that I can obtain a smaller, lighter weight and less expensive power unit by combining the features of a contrarotating rotor of both the compressor and turbine sections and utilizing helium as the working medium. Additionally, in accordance with this invention the thrust loads are reduced resulting in a lighter rotor and the critical speed improved because of the rotor being shorter. The compressor stages are of the axial flow type although the last stage may be a centrifugal type, and the turbine rotor likewise is axial flow although the first stage may be of the radial inflow type. A split scroll is centrally located between the compressor and turbine section and serves to direct compressed helium to the heat source and the high energy heated helium from the heat source to the turbine. The machine is made efficacious because it is possible to accommodate wide chord blades that have sufficient capacity to transmit the necessary torque to the outer of the concentrically mounted rotors.